The statements in this section merely provide background information related to the present disclosure and do not constitute prior art.
Exhaust gas discharged from an engine contains a large amount of hazardous substances such as CO, HC, and NOx. Focus on the serious problem of air pollution caused by the exhaust gas discharged from the engine has become urgent, and thus exhaust gas emission regulations have become stricter in many countries. To meet the exhaust gas emission regulations in each country, many methods and apparatuses for purifying exhaust gas have been proposed, and particularly, many efforts have been made in order to remove NOx which is known as a substance that greatly affects the air pollution among the substances contained in the exhaust gas discharged from a vehicle. As one method, recently, exhaust gas recirculation (EGR) is widely used. The EGR recirculates a part of the exhaust gas into a combustion chamber of the engine and lowers a combustion temperature of the engine, thereby reducing the occurrence of NOx. An EGR apparatus includes an EGR line that extends from an exhaust line of the engine to an intake line of the engine, and an EGR valve is provided in the EGR line in order to adjust the amount of exhaust gas recirculated and introduced into the intake line in accordance with an operation condition. The EGR valve adjusts the amount of exhaust gas recirculated into the intake line by adjusting an opening degree of the EGR line.
In general, as a control algorithm of the EGR valve, PI control or PID control is used to adjust the opening degree of the EGR line by controlling an operation of the EGR valve by combining proportional control, integral control, and differential control. These kinds of control may be expressed as a control function, and the control function includes control parameters such as a proportional gain Kp, an integral gain Ki, and a differential gain Kd. Optimized gains, which are adjusted in accordance with various operation conditions, are required to improve responsiveness of the engine and ensure stable behavior of the engine. However, in the related art, there is a need for engineers trained to tune the EGR valve and control tests need to be performed under many operation conditions, and as a result, there is a problem in that efficiency deteriorates. In addition, the gains are generally used only for the designated engine, and as a result, there is a problem in that a lot of effort needs to be made to set a new gain and adapt the new gain to an operation condition even though the engine is slightly changed.